Is that an inherent fact of prostitution or a function of prostitution's dubious legal status?
One could make similar arguments about ultra-violent criminal cartels and marijuana in the past. "Smoking cannabis isn't distinct from funding Los Zetas in practice"
http://eprints.lse.ac.uk/45198/1/Neumayer_Legalized_Prostitu... "This paper investigates the impact of legalized prostitution on human trafficking inflows. According to economic theory, there are two opposing effects of unknown magnitude. The scale effect of legalized prostitution leads to an expansion of the prostitution market, increasing human trafficking, while the substitution effect reduces demand for trafficked women as legal prostitutes are favored over trafficked ones. Our empirical analysis for a cross-section of up to 150 countries shows that the scale effect dominates the substitution effect. On average, countries where prostitution is legal experience larger reported human trafficking inflows. "
Have to wonder if the scale effect dominating the substitution effect hints that perhaps the Swedish model is optimal for reducing trafficking wholesale while reducing harm (i.e. Johns need strong disincentives in order to not be terribly indifferent people in aggregate) They suggest that the Swedish model reduces the scale effect but not enough data to say if it increases the substitution effect.